<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 200px;
            height: 200px;
            background-color: pink;
        }
    </style>
    <script src="jQuery.min.js"></script>
</head>

<body>
    <div>我是div</div>
    <script>
        $(function () {
            // console.log($("div").css('width'));
            // $("div").css('width', '300px');
            // $("div").css('width', '300');
            // $("div").css(height, '300px'); 属性名一定要加引号
            $("div").css({
                width: 300,
                height: 400,
                backgroundColor: 'red'
            })
        })
    </script>
</body>

</html>